1. Field of the Invention
The present invention relates to flat-panel display devices such as liquid-crystal display devices. The present invention also relates to electronic apparatus comprising the display device.
2. Description of the Related Art
Recently, display devices have been widely used as information-display terminals for portable apparatuses, home use, offices, factories, automobiles, etc. In particular, liquid-crystal display devices are characterized in that they are thin and light and that they use a low voltage and consume low power. Accordingly, liquid-crystal display devices are the main electronic displays in the present and in the future. Liquid-crystal display devices are being increasingly used in personal digital assistants, etc., which take advantage of their low-consumption-power characteristics.
As shown in FIG. 7, an example of conventional liquid-crystal display devices is a passive-matrix liquid-crystal display device or an active-matrix-liquid-crystal display device 1 that uses, as switching devices, two-terminal non-linear devices such as thin film diodes (TFDs). The liquid-crystal display device 1 generally includes a liquid-crystal display panel 2 and a printed-circuit board 3. The liquid-crystal display panel 2 and the printed-circuit board 3 are electrically connected via two flexible printed-wiring boards 4 and 5.
The liquid-crystal display panel 2 has a pair of glass substrates 6 and 7 disposed opposite to each other. The glass substrates 6 and 7 have liquid crystal sealed therebetween. On the opposed internal surface of the glass substrate 6, a plurality of signal electrodes 8 are formed in parallel with one another. On the opposed internal surface of the glass substrate 7, a plurality of scanning electrodes 9 are formed perpendicularly to the signal electrodes 8.
In a predetermined margin (the lower side in FIG. 7) of the liquid-crystal display panel 2, an edge of the glass substrate 6 extends (the bottom in FIG. 7) further than an edge of the glass substrate 7. In a margin (the left side in FIG. 7) of the liquid-crystal display panel 2 which is adjacent to the predetermined margin, an edge of the glass substrate 7 extends further than an edge of the glass substrate 6. In an extended area 6A on the opposed internal surface of the glass substrate 6, data-signal driver integrated circuits (ICs) 10 and 11 are mounted by chip-on-glass (COG) mounting. These data-signal-driver ICs 10 and 11 are connected to output terminals 8A formed by extending the plurality of signal electrodes 8 and to input terminals 12 provided at an edge of the extended area 6A. In an extended area 7A on the opposed internal surface of the glass substrate 7, a scanning driver IC 13 is mounted by COG. The scanning driver IC 13 is connected to output terminals 9A formed by extending the scanning electrodes 9 and to input terminals 14 provided in an edge of the extended area 7A.
The output terminals 4A of the flexible printed-wiring board 4 are bonded so as to be electrically connected to the input terminals 12, which are provided along the longer side of the extended area 6A of the glass substrate 6. Similarly, the output terminals 5A of the flexible printed-wiring board 5 are bonded so as to be electrically connected to the input terminals 14, which are provided along the longer side of the extended area 7A of the glass substrate 7. The input terminal portion 4B of the flexible printed-wiring board 4 is joined to an output terminal portion 15 formed on the printed-circuit board 3 as a control circuit board. The input terminal portion 5B of the flexible printed-wiring board 5 is joined to an output terminal portion 16 formed on the printed-circuit board 3. On the printed-circuit board 3, a predetermined wiring arrangement is formed, and various electronic components for controlling and driving the liquid-crystal display panel 2 are mounted.
One of electronic apparatuses using a liquid-crystal display device having the above-described structure includes input devices such as a key board or a ten-key pad, and uses a liquid-crystal display panel to display data in accordance with input operations from the input devices. In this electronics apparatus, the liquid-crystal display panel and a printed-circuit board are built in a chassis (panel accommodating frame). In this construction, two flexible printed-wiring boards are bent so that the printed-circuit board is positioned behind the liquid-crystal display panel.
In the above-described liquid-crystal display device, as shown in FIG. 8, the printed-circuit board 3 as a control circuit board is provided on the back surface of the liquid-crystal display panel 2. Thus, an overall thickness of the liquid-crystal display device increases and so does a thickness of the display unit for the electronic apparatus. Accordingly, the printed-circuit board 3 hinders thickness and weight reduction of the liquid-crystal display device and the electronic apparatus. In cellular telephones and portable information apparatuses such as portability-emphasized, pocket-sized personal computers, casing thickness must be reduced to its minimum. This problem, in which a control-circuit board hinders the casing thickness from being reduced, occurs not only in a passive-matrix liquid-crystal display device and an active-matrix liquid-crystal display device using the above-described two-terminal non-linear devices but also in various display devices such as an active-matrix liquid-crystal display device having a thin film transistor at each pixel, and an electroluminescent display device. For portability and mobility, it is required that various display devices including a liquid-crystal display device be reduced in weight and thickness. With this requirement, electronic components for driving a display are difficult to mount at high density in limited size and weight.
As shown in FIG. 7, in the above-described liquid-crystal display device 1, the flexible printed-wiring board 4 to be bonded to the extended area 6A of the glass substrate 6 on which the data-signal driver ICs 10 and 11 are mounted, and the flexible printed-wiring board 5 to be bonded to the extended area 7A of the glass substrate 7 on which the scanning driver IC 13 is mounted, must be separately bonded to the printed-circuit board 3. This complicates a modularizing step, and causes a lack of convenience. In addition, since the flexible printed-wiring boards 4 and 5 must be separately bonded to the printed-circuit board 3, it is not preferable that the output terminal portions 15 and 16 formed on the printed-circuit board 3 are too close to each other. In other words, when the flexible printed-wiring boards 4 and 5 are bonded to the printed-circuit board 3 by using a mounting apparatus, a distance preventing the flexible printed-wiring boards 4 and from interfering with each other must be provided. In this construction, the use of a plurality of (two) flexible printed-wiring boards 4 and 5 hinders the size reduction of the printed-circuit board 3.
An input-wiring means 17 for inputting control signals must be connected additionally to the printed-circuit board 3. This complicates terminal connection processing.